Method of making bellows folds



Jan. 19, 1932. w. B. CLIFFORD 1,842,148

METHOD OF MAKING BELLOWS IfOLDS v Filed Sept. 23, 1927 2 Sheets-Sheet 1 Jan. 19, 1932. w. B. CLIFFORD 1,842,148

' mmuon OF MAKING BELLOWS FOLDS Filed Sept. 23. 1927 2 Sheets-Sheet 2 Patented Jan. 19, 1932 =WALTER B. cmrronn, or omnnmen, massaonosnrrs METHOD OF MAKING IBELLOWS IOLDB Application filed September 23, 1927. Serial No. 221,571.

lows folds in thin-wall tubing by a series of rolling or spinning operations, the thin wall of the cylindrical tube being first bulged outwardly to form a series of shallow, rounded portions separated by relatively narrow, un-

corrugated portions. Thereafter the successive corrugations are deepened and narrowed by rolling operations until the finished bellows folds result. It has also been suggested that the preliminary bulging of the thin-wall tube be accomplished by internal pressure exerted hydraulically, and that thereafter the completion of the bellows folds be accomplished through the usual rolling or spinning method. Although the foregoing spinning operation is successfully carried out in commercial practice, nevertheless it is open to certain serious and important disadvantages which are well known and understood by those skilled in the art. Among other disadvantages may be mentioned the uneven working of the walls, due to the contacting of the rolls therewith, and consequent unrqual strains upon the metal and the possibility of compacting pinholes previously contained in the tube in such a manner as to cause subsequent failure during the use of the bellows.

I have devised a method and apparatus for forming these bellows folds in one operation through the employment of liquid pressure within the tube during the forming operation and the application of forming pressure exerted in a direction to contract the tube lengthwise. This operation results in .a uniform product, free from pinholes or similar imperfections, which at present cause failure during the forming operation, and a product which compares favorably with the best product roduced by the rolling method.

The object of the present invention is to provide a new and improved method which produces a bellows having definite and important advantages as compared with bellows madle by any of the methods hereinbefore recite According to the present method, the thinwall tube is first subjected to a rolling, spinning or swaging operation by virtue of which a series of uniformly spaced depressions or grooves is formed in the tube, these grooves being formed by forcing the wall of the tube inwardly throughout restricted areas. Thereafter the grooved tube is inserted in an apparatus having a series of separable forming dies which engage with the uniformly disposed grooves. The interior of the grooved tube is subjected to a hydraulicsustaining pressure, and subsequently a contracting pressure exerted endwise of the tube causes the previously unformed portions of the tubes between the grooves to roll up between the dies into bellows folds. It has been found in actual practice that bellows thus formed are more easily flexed and livelier than bellows made by any method heretofore known. Furthermore, by virtue of the initial inward rolling of the tube followed by an outer bulging of the tube between the rolled areas, the depth of the individual folds which may be produced from a tube shell of given diameter is increased as compared with bellows made by other methods. I am not fully informed as to the reason for the improved flexibility of this type of product, but consider that the improvement is due in part to the temper placed in the inner bends of the bellows folds by the initial rolling operation and to the contracting of the metal thereby, and to a lesser degree is caused by the increased depth of the folds themselves, due to the combined operations. It will be evident to those skilled in the art that according to methods heretofore described, the least amount of temper or work is placed upon the inner bend. Inasmuch as during the performance of the bellows the inner bends are subjected to as great, if not greater, stresses than the outer bends, this portion of the bellows constitutes areas of weakness which may well shorten the life and facilitate failure. According to the present method, the rolling or spinning operation, grooving or bulging the thin-wall tube inwardly along annular lines initially works the portion of the tube which subsequently forms the inner bends, and thereafter the forming of the bellows folds hydraulically progressively works the wall of the tube outwardly toward the outer bends. With this method, the greatest work is imposed upon the inner and outer bends upon which fall the heaviest duty. During the formation and completion of the bellows folds hydraulically there is no frictional engagement or contacting with the straight portions of the walls connecting the inner and outer bends, whereas during the completion of the bellows by the orthodox spinning or rolling methods, the frictional engagement between the closely spaced spinning rolls may well cause an extreme working in localized areas where not desirable.

In the accompanying drawings illustrating diagrammatically one method of performing the present invention,

Fig. 1 represents a method of forming the uniformly spaced annular grooves for a thinwall tube;

Fig. 2 is a similar view at right angles to Fig. 1, illustrating the manner in which the grooving roll approaches the recessed arbor;

Fig. 3 is a diagrammatic view illustratlng the completion of one groove and the start of the next succeeding groove;

Fig. 4 shows the tube advanced to complete a roove already initiated;

ig. 5 illustrates the method of supporting the grooved tube in the separable die plates; and

Fig. 6 illustrates the completed bellows with end fittings attached thereto.

According to the illustrated embodiment of the invention, a thin-wall tube 10 of the desired diameter is loosely supported upon a cylindrical arbor 12 of substantially smaller diameter, having a series of uniformly disposed annular recesses or grooves 14 therein. Cooperating with the arbor is a grooving roll or tool 16 havin two annular ribs 18 and 20 thereon of dissimilar depth, the spacing of the ribs corresponding to the desired spacing of the rooves in the tube. In operation the groove roll is moved transversely to the axis of the arbor to cause the rib 20 of greater depth to initially contact with the tube opposite one of the grooves 14 in the arbor. Continued feed of the ribbed roll thereafter forces the wall of the tubing inwardly into the groove in the arbor to produce an annular recess of the desired depth. Approximately at the completion of the feeding movement, the second rib 18 contacts with the tube and slightly indents the latter in a manner to start the formation of the next succeeding groove, as shown in Fig. 3. Thereafter the tube is advanced upon the arbor an amount equal to the space between the grooves to position the partially formed groove opposite the first mentioned rib 20. as shown in Fig. 4. The foregoing operation is then repeated, the rib of greater depth contacting with the partially formed groove and completing it. It will be evident from the drawings that the grooves in the arbor are of greater depth than the rib 20 upon the spinning roll, so that there is no actual bottoming of the rib within the groove and the annular recess is formed by a swaging or drawing action. Furthermore, inasmuch as the complete formation of each inwardly extending groove is formed individually, the tube is free to contract lengthwise and is not unduly stretched or thinned throughout the grooved areas.

If so desired, the grooved tube may be provided with end fittings, as indicated at 30 and 32, these end fittings being secured to the ends of the tube in a manner to hermetically seal the tube, one of the fittings having an opening therethrough communicating with the interior of the tube for the introduction of internal fluid pressure. The tube thus grooved with highly worked areas corresponding to the inner bends of the completed bellows, is next placed within the separable dies 22 of a machine such as disclosed in my application, No. 1,689,620, dated October 30, 1928. The individual dies lie within the pre-formed grooves, and when closed are locked in uniformly spaced relation lengthwise of the tube. Thereafter internal, sustaining pressure is applied within the tube, and the completion of the folds is carried out in the usual manner, as described in the application referred to. It will be evident tot-hose skilled in the art that by employing a previously grooved tube in this manner, the dies are accurately spaced without the necessity for spacing members within the machine, and that the formation of the ooves tends to initiate the bulging or formation of the bellows folds hydraulically.

The result is to produce a thin-wall bellows having the greatest work imparted at the inner and outer bends where needed. and the least work throughout the straight portion of the walls connected to the bends. In addition, I have produced a bellows tubing having a greater depth of convolution as contrasted with the initial diameter of the tubing than can be satisfactorily obtained by any existing method previously known. Furthermore, bellows having the highly worked areas at the inner and outer bends are free from any undesirable thinning of the metal wall throughout these areas of greatest stress which may impair and weaken the bellows at these points. The result is to produce a bellows having a marked increase in flexibility as compared to a bellows made by other methods, and a liveliness and resiliency which compares favorably to bellows made by the other known method.

What is claimed is:

1. The method of forming bellows folds in tubing which consists in mechanically rolling a series of uniformly spaced and depressed grooves in a thin-Wall tube, assembling the grooved tube within freely movable and se arable die plates engaging with the tube in t e pre-forme'd grooves and spaced solely through such engagement and thereafterforming and completing the bellows folds hydraulically.

2. The method of forming bellows folds in tubin which consists in roducing a series of annular depressions in the tube, mounting an end fitting upon the tube, inserting the tube within separable dies lying in the previously formed recesses and spaced thereby, and forming bellows folds by combined internal fluid pressure and endwise pressure tending to contract the tube lengthwise.

3. That step in the method of forming bellows folds in tubing which comprises mounting a previously grooved tube within freely movable and separable die plates with the die plates lying in the grooves and spaced solely thereby, and subjecting the tube to internal fluid pressure and endwise contracting pressure to produce bellows folds between the grooved areas.

4. The method of forming bellows folds in thin wall tubing which consists in rolling a series of uniformly spaced and depressed grooves in a thin wall tube, one groove being located adjacent the open end of the tube and forming a shoulder in proximity thereto for the reception of an end fitting, assembling separable dies about the tube and engaged therewith in predetermined spaced relation through contact with the grooves, and thereafter forming and completing bellows folds by the combined forces of internal fluid pressure and endwise contracting pressure, the dies collapsing with contraction of the tube due to engagement therewith.

5. The method of forming bellows folds in thin wall tubing which consists in successively rolling from adjacent an open end of the tube a series of uniformly spaced and depressed grooves of suflicient depth to receive and position dies, the groove adjacent the open end forming a shoulder for the reception of an end fitting, assembling dies about the tube received in the grooves and spaced thereby, and thereafter forming and completing bellows folds through the combined forces of internal fluid pressure and endwise contracting pressure, the dies collapsing with contraction of the tube due to their engagement therewith.

6. The method of preparing a thin wall tube for the formation of bellows folds hydraulically which consists in superimposing the tube over an arbor having a series of spaced and depressed grooves and bringing a rotary forming tool having a plurality of spaced forming projections of graduated depth into contact with the tube to form an initial groove adjacent the open end, and thereafter forming successive grooves by a relative movement of the tube and forming tool, a projection of the tool in each case engaging with the last formed groove to further complete the groove and position the next succeeding roove.

7. The metho of preparing athin wall tube for the formation of bellows folds h draulically which consists in supporting t e tube, forming a oove adjacent the open end with a rotary orming tool having a plurality of spaced forming rojeotions of graduated depth, and thereaflier forming successive grooves, a projection of the tool in each case engaging with the last formed groove to further com lete the groove and position the next succee ing oove.

8. The metho of preparing a thin wall tube for theformation of bellows folds hydraulically which consists in forming a depressed groove adjacent the open end of the tube, and thereafter successively forming similar grooves spaced lengthwise of the tube, the last formed groove being deepened and completed and the next succeeding groove being initiated at each operation.

WALTER B. CLIFFORD. 

